| Recently, the study about confined polymer has attracted considerable attention. The confined biopolymer is an ubiquitous phenomenon in biological systems. Biopolymer is usually complete a variety of life activities in confined environment. When confined within a certain range, the conformation of the polymer system and its dynamic property will change dramatically. In addition, the helix is very common structure in confined environment of the organism, which is existed in biological macromolecules, DNA, protein, starch, cellulose. There is evidence that semiflexible polymer binding to cylindrical surface can spontaneously develop helical conformations. Recently, M.Mulder studies the structure of confined polymer brushes within the cylinder by a cylindrical polymer brushes so-called "bottle-brush" model, which backbone chain is also develop ordered helical structure.Hince,if "bottle-brush" binding to cylindrical surface can develop helical conformations caused our attention.In our work, an molecular dynamics simulation method is used to study the conformational behavior of cylindrical polymer brushes confined to a infinitely long cylindrical surface. We choose the model of a linear flexible backbone chain to which semiflexible side chain of equal size are attached at regular spacing. This type of polymer model is similar to the so-called "bottle-brush" polymer.In order to reflecting the impact of the cylindrical polymer brushes in confined environment,we only consider the week adsorption between cylindrical polymer brushes and cylindrical surface.The stiffness of the side chain can be described by bending energy.In our research, we observe the cylindrical polymer brush coli-helix phase transition in different circumstances mainly by changing the grafted number of sider chain, the stiffness of the side chain and the value of week adsorption force and further discussing the helical structure of cylindrical polymer brushes from relevant parameters.1. the stable conformations of backbone chain of cylindrical ploymer brushes confined in the infinitely long cylindrical surface can be impacted by grafted number of sider chain. When only backbone chain (grafted number of sider chain l=0)confined in the infinitely long cylindrical surface, backbone chain curled up into a ball with no order. If grafted number of sider chain add to l=400,stable conformations of the backbone chain of the cylindrical polymer brushes formed a local helical conformation. When grafted number of sider chain continue increasing to the maximum l=1200, the backbone chain surround with cylindrical surface develop a perfectly helical structure, all of the backbone monomers are involver in a helical conformations.2. the stable conformations of backbone chain of cylindrical ploymer brushes confined in the infinitely long cylindrical surface can also be impacted by the value of week adsorption force.The backbone chain can develop a good helical conformations only in the short range near0.2of the value of week adsorption force, otherwise, the helical conformation will be destroyed.3. the stable conformations of backbone chain of cylindrical ploymer brushes confined in the infinitely long cylindrical surface can also be impacted by the stiffness of the side chain. The stiffness of the side chain has little effect on the entire system helical structure, but has some impact on local helical structure.With the stiffness of the side chain incerasing, the helical number and percentage of content of the backbone chain increased to the maximum and then decreased.4. Only in the case of grafted number of sider chain l=1200, the stiffness of the side chain b=100and the value of week adsorption force Do=0.2, does the backbone chain of cylindrical polymer brushes have a perfect helical structure.We expect our study of the conformational behavior of cylindrical polymer brushes confined to a infinitely long cylindrical surface may provide some help and advices to the experiment of cylindrical polymer brushes combined with carbon nanotubes. |
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